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| CSIRO | SOLVE | Issue 6 Feb 06 | |
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COVER STORY
SPRAY COATINGS:
Cold Gold - Cool Moves By Tony Kaye and Rebecca Thyer
A new process has the potential to save money, help the environment and replace electroplating. A Sydney-based engineering company has invested more than $1 million in a new Melbourne production plant just so it can be closer to researchers whose technology could revolutionise its business. The Kirk Group, which specialises in printing systems, has just opened a new plant at Mulgrave in Melbourne’s south-east, near to scientists at CSIRO Manufacturing and Infrastructure Technology at Clayton who developed a technique for manufacturing printing rollers. Using a ‘Cold Spray’ process, the new technique replaces conventional electroplating. It allows metallic and non-metallic powders, or a mixture of them, to be sprayed on to surfaces at supersonic speed and at much lower temperatures than current thermal spray techniques. The advantage of Cold Spray is that the process is more efficient, cost-effective and environmentally friendly. The development is considered a world first. Researchers, and the Kirk Group, believe it could be the next step-change in engineering coatings used to protect many surfaces against wear, corrosion and oxidation, because it avoids a swathe of high-temperature side-effects, which can be costly economically and environmentally. Kirk Group managing director Graeme Kirk says the technology could save his company millions of dollars a year by replacing the electroplating processes used to prepare the rollers used in the printing industry. The Cold Spray technology produces coatings with a gas-jet temperature that is lower than thermal spray processes such as powder flame, wire arc, plasma arc and high-velocity oxygen fuel spraying.
She says it might be more appropriately called 'room-temperature spray' technology because particles are applied at temperatures much lower than the melting temperature of not just the coating, but the substrate as well. “This revolutionary technology avoids a raft of high-temperature effects such as oxidation, vaporisation, melting, crystallisation, residual stresses and gas release. Not surprisingly, we say that it is the next milestone for the thermal spray industry.” Its low temperature means the technology is useful for the 70 per cent of materials that could be spray-coated but are ruled out by the high temperatures required by current thermal technology. The Kirk Group, which employs 92 people and supplies pre-press imaging equipment to printers in Australia and New Zealand, plans to use the technology to produce printing cylinders. “We’re working with CSIRO using their Cold Spray facilities to develop coatings, which we are trialling in our plant,” Mr Kirk says. “So far, they’re proving successful and we’re hoping to replace electroplating with the Cold Spray process.” The Cold Spray technology could halve Kirk’s electroplating costs. “But we need a very, very tight grain structure, and that’s where the difficulty comes in. However, CSIRO scientists are doing a really good job in addressing that. Greame Kirk: “We currently use a lot of chemicals and energy and cutting back on these will make the process very successful.” “There’s still a way to go to prove the success at industry scale but I’m optimistic. It’s very exciting, quite promising. “The major advantages for us are that we get rid of chemicals in our process. This will replace the conventional electroplating, which is not terribly environmentally friendly and is also a big energy and water user. “We use a lot of electricity and water and we use a lot of harmful chemicals, and we have a recycling problem with the things we use because we are using a lot of heavy metals and copper sulphates and acids.” Dr Jahedi says the Cold Spray research has been focused not only on developing advanced coatings but using the technology for defect repair and direct fabrication. Direct fabrication and near-net shape manufacturing have been subjects of interest and investigation for years, with several emerging technologies being developed, such as laser-engineered net shaping, direct light fabrication and selective laser sintering. “These technologies are attractive because they can potentially cut time and costs incurred for rapid prototyping, and perhaps for small-lot production. “However, there are inherent difficulties that have hindered their widespread adoption – all involve melting and solidification and have problems associated with that.” This is where Cold Spray technology could also have an impact. It is opening new doors to permit direct fabrication of near-net shapes of metals, composite and polymeric materials, at or near room temperature with little or no melting. Dr Jahedi believes the Cold Spray technology will have a huge impact on manufacturing in Australia. “We’re introducing Australian industry to a world-class technology that will not only make them more competitive on the world scale, but will also benefit the environment.” Mr Kirk says the environmental advantages of the process will make it popular all around the world. “We currently use a lot of chemicals and energy and cutting back on these will make the process very successful.” Dr Jahedi says there are useful applications for the Cold Spray technology in just about any industry, from biomedicine to aerospace and chemical and mineral processing, and for applications in the electronics, paper, oil, gas and glass industries. CSIRO is working on different applications for this technology with companies such as alumina mining and aluminium production giant Comalco, a division of Rio Tinto. Trials of the newly developed processes are already under way, with the technology having the potential to save some companies many millions of dollars by eliminating existing, costly processes. For the Kirk Group, the next test is to successfully scale-up the unit being used at CSIRO. “We need to prove the commercial-scale plant is successful, which I’m confident about,” Mr Kirk says. “At the moment we’re doing it at one-tenth of the scale needed and obviously we need to increase this.” APPLICATION A ‘Cold Spray’ process allows powders to be sprayed on to surfaces at high speeds, replacing conventional electroplating For further information contact: |
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CSIRO’s Cold Spray and Tooling team leader, Dr Mahnaz Jahedi, pioneered the introduction of the Cold Spray technology, or cold gas-dynamic spray technology, to Australian industry two years ago, making possible easy access to the development of cold-sprayed, exotic coatings.
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